This invention relates to a polyol resin derived from epoxy resin and process for preparing the same, and more specifically relates to a polyol resin which possesses flexibility, high crosslinking reactivity and high storage stability and is suitably used for baking type coating material, or the like.
Among bisphenol type epoxy resins, those having high molecular weight have considerable amounts of secondary hydroxyl groups in their molecular chains and hence can be considered to be a type of polyol resin. It has been, therefore, known that a bisphenol type high molecular weight epoxy resin is used as the polyol component of polyurethane paint.
Nevertheless, the film of coating finally formed in such paint is brittle due to the toughness inherent in bisphenol type epoxy resin. Moreover, coating compositions whose baking cycles are short, that is to say, whose curing time is short, is desirable in setting up an energy-efficient coating process line. Emergence of such a polyol component which imparts a higher reactivity has, therefore, been desired.
Moreover, high molecular weight epoxy resin cannot be used for the coating material which is used in a compounded form with tar or asphalt, since the epoxy group contained therein, small as it may be in amount, would still increase the viscosity of the paint after a lapse of time in the case the paint, is mixed with tar or asphalt, to the extent that the storage stability of the paint is impaired.